Process of drying products produced from aqueous dispersions of organic substances particularly of caoutchouc or caoutchouc like substances by agglomeration upon a base



Patented Get. 6, 1931 PATENT, OFFICE uNiTEDr STATES PAUL KLEIN, OF BUDAPEST, HUNGARY, ASSIGN T0 AMERICAN ANODE INCL, OF

. AKRON, OHIO V s PROCESS or DRYING PRGDUCTS rnenncrn more "AQUEOUS DISPERSIONS or ORGANIC SUBSTANCES PARTICULARLY or ceonrcnouc on cnon'rcnonc LIKE SUBSTANCES BY AGGLOMERATIQN UroN A ase No Drawing. Application filed January 16,1828, Serial No. 247,267, and in Germany January 17, 1927.

This invention relates to a process" for drying products produced from aqueous dis-1 persions of organic substances particularly of caoutchouc or caoutchouc like substances by agglomeration upon a base, 7 1

As is well known, the dispersed substances in aqueous dispersions of organic substances, for example natural caoutchouc latex, or artificial caoutchouc dispersions, can be agglomerated upon suitable bases, by concentrating the dispersed substance from the dispersion liquid onto a deposition base.

Such agglomeration can for example be efiected upon suitable absorbing bases, for example upon porous moulds, impregnated with coagulating agents, by continued dipping or by electrophoretic means. Deposits thus obtained may either directlyhave the shape of the finished article'or may be further moulded.

The aforesaid methods have the advantage that by means of a single dipping e. in one operation, without repeated dipping and drying), deposits of considerablethickness can be produced, which are homogeneous throughout i. e. which do not exhibit any formation of layers. Nevertheless deposits produced in this manner contain a considerable amount of moisture. When working up substances which on drying incline to skin formation i. e'., which more or less lose their permeability to water, the moisture can only be removed with difliculty, from the relativelythick layers which come into question, because the superficial layer which dries first, loses its permeability to water and retains moisture in the interior of the deposit.

The present invention aims at providing a process which is adapted to facilitate the drying of such products even if they are of considerable thickness.

According to the invention a higher temperature is maintained during the drying, at that side of the layer to be dried, which is opposite to or remote from the side which permits the escape of the moisture, than at the other side.

Inasmuch as the process is primarilyintended to be employed for caoutchouc, the

process will hereinafter be described by way example in its application to caoutchouc.

The products obtained from caoutchouc latex or other aqueous caoutchouc dispersions byagglomeration of the caoutchouc from the dispersion upon deposition moulds or bases can either be dried on the deposition mould itself, or when the caoutchouc deposit has already been removed from its deposition base. i

In the former case, two. possibilities again comeinto consideration, according to whether deposition-moulds impermeable to liquids for example of metal,'or Whether porous deposition moulds, for example of'unglazed clay, are employed.

If, when employing metallic deposition moulds,"the drying is to'be efi'ected on the mould itself, only one side of the caoutchouc deposit is exposed to the air and the moisture can only escape at this exposed side, whilst the other side of the caoutchouc deposit lies on the metal mould, which thus prevents the escape of moisture at that side. in carrying out the invention, the drying is efiected by heating the metal mould. By this means the drying of the caoutchouc deposit commences at the innermost layer in contact with the metal mould whilst drying of the caoutchouc on the outer surface of the caoutchouc deposit which is exposed to the freeair, is delayed in comparison with the drying at the side which is in contact with the mould in such a manner that the escape of the moisture driven out by heat ing the mould, is not or at least not essentially impeded. For this purpose the tema peratureof the air sweeping around the caoutchouc object to be dried, is maintained at a lower degree than-the temperature of the innermost layer which is in contact with the deposition mould. The watervapour escaping from the caoutchouc is gradually withdrawnby the movement of the air at the outer side of the'mould which is in contact with the rubber. The drying at the outer exposed side can be also delayed by causing'the air sweeping around the exposed surface of the caoutchouc articles to be dried, to contain ab initio, a certain amount of moisture.

When porous deposition moulds are employed the heating may likewise be effected at the side in contact with the mould in a similar manner as in the case of metallic moulds. However, since when using porous deposition moulds, the moisture can escape not only from the outer surface of the caoutchouc deposit, but also, through the (pores of the mould, from the innermost si e in contact with the mould, the drying may also be efiected by heating the air sweeping around the outer side of the caoutchouc de posit, if provision is made for the removal of the vapours from the innermost side of the caoutchouc deposit in contact with the mould and if the drying of the deposit at this side is impeded as much as possible.

Although the deposition moulds may be heated by means of heated liquids or steam, it is preferable to employ heated air for this urpose. \Vhen drying upon deposition ses, these may advantageously be heated for example by resistance heating, or when employing metal moulds, particularly iron moulds, electrically, by induction, by means of alternating current.

In cases where the drying is effected after removal of the deposit from the deposition mould for example when producing endless caoutchouc bands, the band may be heated on one side whilst the temperature at the other side of the band is maintained at a lower degree and the drying at this latter side is delayed.

Altho h the process is primarily intended for articles produced from vulcanized or unvulcanized caoutchouc latex by electrohoretic deposition from caoutchouc latex, if desired in admixture with additional substances (such as vulcanizing agents, accelerators, dyes, fillers and the like) it may also be applied to articles produced from artificial caoutchouc dispersions, or from dispersions of gutta-percha, balata and other analogous ve etable resins, as well as in the production o l articles from dispersions of other organic substances such as for example casein, albumen, cellulose esters, artificial and natural resins and the like, which on dr ing incline to skin-formation or which lose t eir permeability to water.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. The process of making a product comprising a layer produced by agglomeration from aqueous dispersions of organic material particularly of caoutchouc or caoutchouc-like substances which on drying become practically impermeable to water, which in-- cludes depositing a layer of said organic material containing a high percentage of water upon a mold, permitting at one side of said layer a relatively free escape of moisture, and maintaining a higher temperature at the side of the layer remote from the side permitting escape of moisture than at the latter side.

2. The process as set forth in claim 1, in which the higher temperature at the side of the layer remote from the side permitting escape of moisture is maintained by heating the mold.

3. The process of making a product comprising a layer produced by agglomeration from aqueous dispersions of organic material particularly of caoutchouc or caoutchouc-like substances which on drying become practically impermeable to water, which includes forming a layer of said organic material containing a high percentage of water, retarding the drying of the layer on one side by subjecting it to an atmosphere comprising water vapor, and applying heat to the other side of the layer.

4. The method of making rubber articles which comprises providing a bath consisting of a dispersion of rubber in water, dispersions or solutions of vulcanizing agents and compounding ingredients, depositing from the material of said bath a layer of rubber on a form in a substantially unheated condition, and drying the layer of rubber so deposited by heating the form from within, and vulcanizing the article so formed.

5. That method of making rubber articles by dipping, which comprises providing a bath consisting of a dispersion of rubber in Water, dispersions or solutions of vulcanizing agents and compounding ingredients, dipping smooth forms in the above bath while at lower than vulcanizing temperatures, drying the films of rubber deposited on the forms by heating the forms from within to lower than vulcanizing temperatures, and vulcanizing the articles on the forms.

6. That method of making rubber articles by dipping, which comprises providing a vulcanizable dispersion of rubber in water, dipping a form in the dispersion, drying the film of rubber on the form by heat applied from within at less than vulcanizing temperatures, and vulcanizing the dried film.

In testimony whereof I allix my signature.

PAUL KLEIN. 

